The research proposed in this grant combines the study of the nutrient related physiology of the gastrointestinal tract with the demonstration of the influence of relevant aspects of this physiology coordinated in feeding behavior. The view that informs this work is that feeding functions to maintain caloric homeostasis in the organism via the mediation of central nervous system mechanisms but must accomplish this goal through the integrated activity of several bodily compartments. The experiments devised here will (1) explore in the rhesus monkey the capabilities of the gastrointestinal tract for the management of intraluminal calories in a coordinated way, (2) relate these capabilities to aspects of meal taking, (3) describe the role of GI hormones such as cholecystokinin and of circulating nutrients in relating the management of calories by the gastrointestinal tract to feeding, and (4) study the effects of interrupting the vagal linkages between the GI tract and the brain on this coordination between gastrointestinal function and feeding.